Step stool



FIG. 1 is a perspective view of the step stool;

FIG. 2 is a upper plan view of the step stool;

FIG. 3 is a side elevation of the step stool;

FIG. 4 is an end view of the step stool; and,

FIG. 5 is a side elevation of the other side of the step stool. 

The ornamental design for a step stool, as shown and described. 